Device for liquefying a gas

Abstract

In order to prevent icing of the cryogen, a device for liquefying a gas includes a heater provided in a cooling chamber at the output of a Sterling cycle engine. The heater is controlled by a gas pressure sensor in the cryostat in communication with the chamber and matches the cooling load to the cooling capacity of the Sterling cycle engine.

What is claimed is: 
     
       1. A device for liquefying a gas, comprising: (a) a vessel containing therein an amount of liquid cryogen and having a space above the surface of said liquid cryogen;   (b) a chamber;   (c) a first conduit for connecting an upper side of an interior portion in said chamber and said space in said vessel;   (d) a second conduit for connecting a lower side of said interior portion in said chamber and said liquid cryogen in said vessel;   (e) a sensor for detecting the pressure in said vessel;   (f) cooling means provided in said chamber for liquefying a gas;   (g) heater means provided around said cooling means in said chamber for producing heat as a function of a quantity of electrical power provided thereto; and   (h) a control device for controlling the quantity of the electric power to said heater means according to a signal from said sensor.   
     
     
       2. A device for liquefying a gas in accordance with claim 1 wherein said cooling means includes a refrigerator having an expansion cylinder which is extended into said chamber and a heat-exchanger mounted to said expansion cylinder. 
     
     
       3. A device for liquefying a gas in accordance with claim 2 wherein said refrigerator is a Stirling cycle refrigerator. 
     
     
       4. A device for liquefying a gas in accordance with claim 1 wherein said chamber is heat-insulated. 
     
     
       5. A device for liquefying a gas in accordance with claim 1 wherein said first and second conduits are heat-insulated.